Quarterly report pursuant to Section 13 or 15(d)

Initial Public Offering - Additional Information (Details)

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Initial Public Offering - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Initial Public Offering [Line Items]          
Net proceeds from Initial public offering excluding underwriting discounts and commissions $ 32,400     $ 32,426  
Loss on remeasurement of convertible preferred stock warrant liability   $ 3,725 $ 551 3,725 $ 551
Reclassification of convertible preferred stock warrant liability into additional paid-in capital $ 5,700     $ 5,711  
Common Stock          
Initial Public Offering [Line Items]          
Conversion of preferred stock into common stock, shares 4,689,753     4,689,753  
Additional Paid-in Capital          
Initial Public Offering [Line Items]          
Reclassification of convertible preferred stock warrant liability into additional paid-in capital $ 42,100     $ 42,100  
Offering cost incurred excluding underwriting commissions and discounts 1,800        
Other Expense, Net          
Initial Public Offering [Line Items]          
Loss on remeasurement of convertible preferred stock warrant liability $ 3,700     $ 3,700  
Maximum          
Initial Public Offering [Line Items]          
Number of shares called by warrant 84,000 84,000   84,000  
IPO          
Initial Public Offering [Line Items]          
Sale of stock, shares 3,220,000        
Price per share $ 11.00 $ 11.00   $ 11.00  
IPO | Maximum          
Initial Public Offering [Line Items]          
Number of shares called by warrant 84,000 84,000   84,000  
Over-allotment option          
Initial Public Offering [Line Items]          
Sale of stock, shares 420,000